Related Experiment Videos
A new in vitro approach for investigating the MPTP effect on DA uptake
1Centre d'études et de Recherche sur les Xénobiotiques, UPRES EA 1223, 34, rue du Jardin des Plantes, BP 199, 86005 Cedex, Poitiers, France.
Abstract:
Previous studies have shown that dopamine (DA) uptake was decreased after preincubation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or 1-methyl-4-phenylpyridinium (MPP(+)) in in vitro slice and synaptosome models. The present study, conducted with and without preincubation, attempted to determine whether inhibition results from a direct effect of neurotoxins on neuronal DA transporter or from an alteration of the transporter secondary to other toxic events. DA uptake was inhibited about 50% in the presence of MPTP+O(2) or MPP(+) (0.1, 1 and 5 mM) in rat striatal slices and synaptosomes. Such inhibition was obtained in synaptosomes preincubated for 150 min with MPP(+) and then washed. Inhibition of DA uptake was lower in slices preincubated with MPTP (5 mM)+O(2) and then washed (30%). Experiments in synaptosomes prepared from slices preincubated with MPTP or MPP(+) showed greater inhibition of DA uptake with MPTP. The results suggest that the inhibition of DA uptake in vitro by MPTP or MPP(+) results initially from a direct effect on the transporter during its penetration in nerve endings and subsequently from a transporter alteration related to toxic events. Thus, the preincubation of striatal slices followed by DA uptake measurement in synaptosomes would appear to be a good in vitro model for studying the dopaminergic toxicity of MPTP.
Insights
Neurotoxins like MPTP and MPP+ directly inhibit dopamine (DA) transporter function. Subsequent toxic events further alter transporter function, impacting DA uptake in brain cells.
Area of Science:
- Neuroscience
- Neurotoxicology
- Molecular Biology
Background:
- Previous research indicates that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its metabolite 1-methyl-4-phenylpyridinium (MPP+) reduce dopamine (DA) uptake.
- The precise mechanism, whether direct transporter inhibition or secondary toxic effects, remains to be fully elucidated.
Purpose of the Study:
- To investigate whether the inhibition of DA uptake by MPTP and MPP+ stems from a direct impact on the neuronal DA transporter or from alterations secondary to other toxic mechanisms.
- To differentiate the effects of MPTP and MPP+ on DA uptake in vitro.
Main Methods:
- Utilized rat striatal slices and synaptosomes to assess DA uptake.
- Compared DA uptake inhibition with and without preincubation of neurotoxins (MPTP and MPP+).
- Investigated the effects of washing synaptosomes after MPP+ preincubation.
Main Results:
- MPTP and MPP+ significantly inhibited DA uptake (approx. 50%) in striatal slices and synaptosomes.
- Washing synaptosomes after MPP+ preincubation still resulted in significant inhibition.
- MPTP showed greater inhibition of DA uptake compared to MPP+ when assessed in synaptosomes derived from preincubated slices.
- Preincubation with MPTP followed by washing showed a lower inhibition (30%) compared to MPP+.
Conclusions:
- The inhibition of DA uptake by MPTP and MPP+ involves an initial direct effect on the DA transporter during nerve ending penetration.
- Subsequent toxic events contribute to further alterations in transporter function.
- The study supports the use of preincubated striatal slices and synaptosomes as a valuable in vitro model for studying the dopaminergic toxicity of MPTP.